After analyzing millions of tweets, researchers have determined April 13, 2013, the day of the Boston Marathon bombings, was the saddest day on Twitter in five years. Previously, December 14, 2012, the day of the Newtown school shooting, held that distinction. 

According to Hednometer, which conducted the research, April 15 was a tax day and a Monday, which made it doubly unbearable. But there was no end to the outpouring of grief on the microblogging site once word got out on the bombings. 

To assess Twitter's highs and lows, Hednometer monitors "a random sampling of roughly 50 million (10%) of all messages" posted each day, according to HuffPost's Craig Kanalley. From there, the site analyzes the 5,000 most commonly used words in the English language, based on various sources, and ranks them on a nine-point scale, from happy (9) to sad (1).

April 15 saw some of the saddest words appear over and over, including "sad," "sick," "injured," "died," "bomb," "tragedy," "blood," "killed," "hate" and "terrible."

According to the analysis, these were the most tweeted words on April 15: 

[via Poynter]